In this review, we will be comparing Crystal 4.2 and S20, two Passive Bookshelf speakers from Wharfedale and Polk Audio.
Let's have a brief look at the main features
of Wharfedale Crystal 4.2 and Polk S20 first before getting into our more
detailed comparison.
| Key Specs | Wharfedale Crystal 4.2 | Polk S20 |
|---|
| Brand | Wharfedale
United Kingdom · founded 1932 | Polk Audio
United States · founded 1972 |
|---|
| Design | 2-way | 2-way |
|---|
| Tweeter | 1" Soft-dome | 1" Soft-Dome |
|---|
| Woofer | 5" Woven Kevlar | 6.5" Mica-reinforced polypropylene |
|---|
| Frequency response | 60-20k Hz | 39-40k Hz |
|---|
| Sensitivity | 88 dB | 88 dB |
|---|
| Impedance | 8 ohms | 8 ohms |
|---|
| Power range | 20-100 watts | 20-125 watts |
|---|
| Weight | 4.20kg / 9.2lbs | 7.73kg / 17lbs |
|---|
| Dimensions (H x W x D) | 10-7/16" x 7-1/8" x 8-5/8"
266.0 x 181.0 x 220.0mm | 14.8" x 8.5" x 13.7"
376.0 x 216.0 x 350.0mm |
|---|
What size room are the Wharfedale Crystal 4.2 and Polk S20 speakers good for?
The size of the room in which you are planning to use these loudspeakers is an important decision
factor. Here we have compared their suitability to various sizes of environments considering their size
and max power parameters:
| Listening Environment* |
Wharfedale Crystal 4.2 |
Polk S20 |
| Near-field |
Average |
Poor |
| Small Room |
Good |
Average |
| Mid-size Room |
Average |
Good |
| Large Room |
Poor |
Average |
| Very Large Room |
Bad |
Poor |
(* Approximate Room sizes: Small < 100sq. ft / 9 m2,
Mid-size: 100-220 sq. ft / 9-20 m2, Large 220-400 sq. ft / 20-36 m2, Very Large: >
400 sq. ft / 36 m2.
Average Floor Height: 9" / 2.7m. Typical room sizes differ from country to country, and the actual
listening experience changes depending on floor height, room shape, surface materials, listening
position, speaker locations, etc.)
The sections below take each area in turn: drivers, frequency response, physical size and what you get in the box.
Drivers
Both Crystal 4.2 and S20 are 2-way speakers.
Wharfedale Crystal 4.2Polk S20
TweeterWoofer
Front view, drawn to scale - cabinets and drivers share one scale, so sizes are directly comparable. Hover a driver for its size.
| Driver |
Wharfedale Crystal 4.2 |
Polk S20 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 5-inch
|
1 x 6.5-inch
|
Crystal 4.2 features a 1" Soft-dome Tweeter and 1 x 5" Woven Kevlar Woofer. On the other hand, the S20 features a 1" Terylene Soft-Dome Tweeter and 1 x 6.5" Mica-reinforced polypropylene Woofer with a Crossover frequency at 2500Hz.
Frequency Response
Crystal 4.2 has a frequency range of 60-20k Hz whereas S20 has a frequency range of 39-40k Hz. With a minimum frequency of 39Hz, the S20 can go significantly deeper on the low side and provide stronger bass compared to the Crystal 4.2's min frequency of 60Hz.
The graph below depicts how these two speakers compare with the max, min and average Low Frequency values of other speakers in the Bookshelf class in our database.
Low Frequency
Bookshelf Speakers
Neither pair reaches down to 20Hz, the usual definition of full-range, which is normal for speakers of this size. If you want the bottom octave for movies or bass-heavy music, add a subwoofer to whichever you choose. Visit our Powered Subwoofers section to find out more about the available options.
Impedance and Sensitivity
Crystal 4.2 and S20 have the same Impedance of 8 ohms and their sensitivity is also same at 88 dB.
Sensitivity
Bookshelf Speakers
Power Range
Power
range is the range of input power in watts RMS that a loudspeaker is designed to handle. Staying
within that range gives nominal performance; driving the speaker beyond its maximum wattage can damage it.
S20 can handle a max power of 125 watts RMS, whereas Crystal 4.2 has a max power handling value of 100 watts RMS, 25 watts less than the S20.
Note that higher power handling does not make a speaker louder: that depends mainly on
sensitivity and impedance. The calculator below shows how loud each of these actually plays
on a real amplifier.
Which plays louder on your amplifier?
Starting with a popular amplifier - change it to the one you own, or any you are
considering, and watch both numbers move.
Input Type and Bi-Amping / Bi-Wiring
Crystal 4.2 features 5-way post posts which make bi-amping or bi-wiring possible. S20 has a 5-way post which doesn't feature bi-amping/bi-wiring.
Cabinet Type and Port Position
Both Crystal 4.2 and S20 have rear firing ports. Rear ported speakers generally need more room between the backside of the speaker and the wall compared to sealed and front/bottom ported speakers. Placing the speakers too close to the walls may cause the bass to sound boomy.
If you are limited in space and can't get the speakers away from the backwall, check our Speakers with Front Firing Ports page.
Physical Specs
The size of a speaker can sometimes be an important decision factor due to space constraints or in some cases purely for esthetic reasons. In this section, we are going to compare Wharfedale Crystal 4.2's and Polk S20's external dimensions. Wharfedale Crystal 4.2 has external dimensions of 266.0 x 181.0 x 220.0mm (10-7/16 x 7-1/8 x 8-5/8inch) whereas Polk S20 has external dimensions of 376.0 x 216.0 x 350.0mm (14.8 x 8.5 x 13.7inch).
Polk S20 is clearly the larger of the two speakers. Its body is 35mm wider, 110mm taller and 130mm deeper than Wharfedale Crystal 4.2.
Below you can see the front view size comparison of Wharfedale Crystal 4.2 and Polk S20 in scale.
Comparison image of Wharfedale Crystal 4.2 and Polk S20 Size and External Dimensions
Base Surface Area Comparison
Base surface area of a loudspeaker may become a determining factor when the space in your room or desk is limited.
The base surface area of the Wharfedale Crystal 4.2 is approximately 398.2cm2 / 61.7inch2 and base area of the Polk S20 is approximately 756.0cm2 / 117.2inch2. The Crystal 4.2 requires 47% less surface area than the S20 which gives it a small advantage on placement in tight spaces.
Here is another comparison that shows both speakers on a BDI Octave Media Cabinet, next to a standard size amplifier and turntable in scale:
Size Comparison image of Wharfedale Crystal 4.2 and Polk S20 on a Media Console
Weight Comparison The weight of a loudspeaker can become an important factor if you need to move and reposition the unit often. Weight of a speaker can also "sometimes" be an indicator of the rigidity of the enclosure and the quality of the internal components used. The Wharfedale Crystal 4.2 weighs 4.20kg / 9.2lbs and the Polk S20 weighs 7.73kg / 17lbs. This makes the S20 84% heavier than the Crystal 4.2.
Here is a comparison of how Crystal 4.2 and S20's weights compare with the average, max and min weights in Passive Bookshelf class.
Weight
All Bookshelf Speakers
What's in the Box of Wharfedale Crystal 4.2?
Here are the items that are included inside the box of Crystal 4.2:
- 2 Bookshelf loudspeakers
- 2 Grilles (pre-installed)
- User-feets Manual
- Installation Guide
What's in the Box of Polk S20?
Here are the items that come with the S20:
- 2 Bookshelf loudspeakers
- 2 Grilles (attached)
- 8 Self-adhesive rubber feet
- Owners Manual
- Online Product Registration
 Bi-Amping and Bi-Wiring |
Yes
vs
No
|
Allows bi-amping and bi-wiring connections |
 Height |
266mm
vs
376mm
|
Easier to fit in smaller spaces |
 Base Surface Area |
398cm2
vs
756cm2
|
Takes less floor space |
 Max Input Power |
125 watts
vs
100 watts
|
Handle more power from your amplifier |
 Woofer Size |
6.5 inches
vs
5 inches
|
Larger woofer |
|
Low Frequency Response |
39 Hz
vs
60 Hz
|
Generates deeper bass |
 High Frequency Response |
40k Hz
vs
20k Hz
|
Generates higher frequency |
 Price per pair* |
299USD
vs
349USD
|
costs less (*prices may change depending on the seller, location and time) |
| General |
Wharfedale Crystal 4.2 |
Polk Audio Signature S20 |
| Brand |
Wharfedale |
Polk Audio |
| Speaker Type |
Bookshelf speakers |
Bookshelf speakers |
| Power Range |
20-100 watts |
20-125 watts |
| Sensitivity |
88 dB |
88 dB |
| Impedance |
8 ohms |
8 ohms |
| Frequency Response |
60-20k Hz |
39-40k Hz |
Drivers |
|
|
| Woofer Quantity |
1 |
1 |
| Woofer Size |
5" |
6.5" |
| Woofer Composition |
Woven Kevlar |
Mica-reinforced polypropylene |
| Woofer Surround Material |
Rubber |
Butyl rubber |
| Tweeter Size |
1" |
1" |
| Tweeter Type |
Soft-dome |
Soft-Dome |
| Aimable Tweeter |
No |
No |
| Midrange Driver |
No |
No |
| Crossover Frequency |
n/a |
2500Hz |
| Firing Direction |
rear |
rear |
Physical Specs |
|
|
| Height |
266.0mm (10.5") |
376.0mm (14.8") |
| Width |
181.0mm (7.1") |
216.0mm (8.5") |
| Depth |
220.0mm (8.7") |
350.0mm (13.8") |
| Weight |
4.20kg (9.2lbs) |
7.73kg (17lbs) |
| Enclosure |
Bass reflex |
Bass Reflex |
| Finish |
Wood-grain vinyl |
Meddite MDF |
| Available Colors |
Walnut |
Black, Walnut, Brown Walnut |
| Mounting Bracket |
No |
No |
| Recommended Stand Height |
24-28" |
24-28" |
| Grille |
Yes |
Yes |
| Moisture Resistancy |
No |
No |
Connections |
|
|
| Biamp Inputs |
Yes |
No |
Other |
|
|
| Parts Warranty |
5 Years |
5 Years |
| Labor Warranty |
5 Years |
5 Years |
No single best speaker here - they are built to different priorities, and the right one depends on your room, your amplifier and what you listen to.
| Area | Better | Why |
|---|
| Bass | B | Polk S20 digs deeper - 39Hz against 60Hz. |
| Amplifier needs | evenly matched | Similar sensitivity (88dB vs 88dB) - both want much the same power. |
| Headroom | B | Polk S20 takes more power (125W vs 100W) - more in hand in a big room. |
| Size | depends | Wharfedale Crystal 4.2 is easier to place; Polk S20 is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | A | Wharfedale Crystal 4.2: bi-amping. |
| Price | B | Polk S20 is cheaper - $299 against $349, about 14% less. |
A Wharfedale Crystal 4.2 B Polk S20
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Polk S20 has the edge on paper, though the margin is not large. The rows marked "depends" may matter more to you than the score does. If a subwoofer is in your plans, the bass gap largely stops mattering - you would be crossing over above 60Hz anyway, so judge these on the other rows instead. Match it to your room: we rate Wharfedale Crystal 4.2 the better fit for near-field listening and a small room, and Polk S20 for a mid-size room and a large room.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.